The United States Submarine Memphis (Figure 1) ran aground
in approximately 10 meter depth on a coral reef off southeast Florida (Figure 2)
February 25, 1993. Extensive physical damage to the reef substrate and injury to
the coral community were attributed to the initial grounding and subsequent
attempts to free the submarine from the impacted reef (Figures 3 and 4). The
impact of the grounding was assessed, and the area of damage was determined
through field and photographic studies.

An impacted area of 2,310 m2 was assessed with 1,205 m2 having been totally
destroyed (Figures 3 and 4). In 1997, the State of Florida was awarded a
settlement of $750,000 by the Federal government for environmental damages
caused by the submarine grounding. A plan to perform hypothesis testing of
restoration techniques was developed and initiated.

Using artificial reefs as experimental platforms, we are examining three
restoration strategies: 1) the potential of enhancing coral recruitment through
the use of coral larval attractants, 2) the effect of reef structure on the
associated fish assemblages, and 3) the interaction between fish assemblages and
coral recruitment and survival.

METHODS:

One hundred and sixty small artificial reef modules (Reef
Balls™) were deployed in 11 m of water on a sand flat between reef tracks
adjacent to the U.S.S. Memphis grounding site (Figure 5). The Reef Balls were
organized into 40, 4-module reef units (quad) in a square configuration having
approximately 4 m sides (Figure 6). The separation of individual Reef Balls (2
m) was judged sufficient to avoid interaction effects between Reef Balls in
terms of coral settlement, but close enough for the 4 balls to function as a
single reef unit in terms of fish recruitment. Each quad was located a minimum
of 30 m from any hardbottom.

Coral Recruitment:

Settlement plates on each Reef Ball (Figure 7) are being
used to test hypotheses on enhancing coral recruitment through the use of larval
attractants. The settlement plates attached to each Reef Ball are treated with a
potential attractant (iron, CaCO3, coral transplants) and compared with control
plates (no attractant). Coral transplants are 4” cores drilled from large donor
colonies (Figures 8 and 9). Eighty coral cores have been transplanted onto the
Reef Ball modules (forty cores of each of two different species). Control corals
occurring on the natural reef, and of comparable size to the donor corals, are
being monitored for comparison of growth and mortality.

Larval Attractants:

Each individual Reef Ball in a quad will incorporate one of four different
attractants on the settlement plates:

Iron additive

CaCO3

Coral transplants

Control

Coral Transplantation and Monitoring:

At quarterly intervals the donor corals, coral transplants, and control
corals are being visually assessed to provide information on individual colony
health, growth, and mortality.

Fish Recruitment:

The 40 quads are divided into 4 different levels of
structural complexity (refuge) to test the hypothesis that multiple refuge size
and the resultant diverse fish assemblages may affect coral recruitment,
survival, and growth. One set of 10 quads has the void space of all the Reef
Balls filled with large refuge structure (Figure 10). One set has the void
spaces of all filled with small refuge structure (Figure 11). Another set is
mixed having one Reef Ball empty, one with large refuge, and the last two with
small refuge. The final set has the void space of all the Reef Balls empty. The
assemblage of fishes (species, number, and size) associated with each quad is
being recorded every three months by visual census.

Artificial reefs are commonly used to provide structure to damaged reef
areas. This project has been designed to use artificial reefs to not only
mitigate for lost reef structure but to provide experimental platforms to
examine several restoration strategies. The examination of these strategies will
aid in making reef restoration decisions that involve:

the potential enhancement of coral recruitment through the use of coral
larval attractants,

the effect of reef structure on fish assemblages, and

the interaction between fish assemblages and coral recruitment and
survival.